Recently, inkjet printers have become increasingly important in numerous applications. While generation of text print documents has remained important, inkjet printers have become increasingly important in generation of photographs created through digital means. The speed and quality with which prints are generated has also become increasingly important as customers continue to raise their expectations. This transformation presented significant difficulties in the formulation of inkjet inks. Unlike previous application, photographs require long term archivability. Instead of lasting for a few weeks or months, photographs are expected to remain unchanged for years or even decades. With increased print speeds and customer expectations, the performance of the ink during printing has become even more critical.
With previous inkjet dye sets, the required degree of permanence has not been readily attained without a negative impact on color. In order to address this issue, new dyes are being employed in the inkjet industry. In order to be successful at attaining the required level of archivability, a careful balance of color and permanence must be obtained for the combination of dyes employed in the ink set.
Another essential quality of inkjet ink that must be addressed is its consistent performance in a printhead. This includes such attributes as start-up, maintenance, and reliability. Since the ink consists primarily of an aqueous medium with additional cosolvents, the compatibility of the dyes employed in the ink with the balance of the ink is paramount importance. Many dyes exhibit excellent color or lightfastness, but are deficient in this required compatibility, which can often be expressed in terms of the aqueous solubility of the dye.
In order to address these divergent requirements, blending of dyes is often required. This invention describes combinations of yellow dyes that sufficiently address these three issues. The resulting inks exhibit excellent permanence, brilliant color, and robust performance in the printhead.
This invention employs two dyes in specific amounts to achieve exceptional results.